Note: Descriptions are shown in the official language in which they were submitted.
CA 02578984 2007-03-05
BED CONSTRUCTION WITH REDUCED SAGGING
BACKGROUND OF THE INVENTION
The present invention relates generally to a bed construction, and more
particularly to a bed construction having a one-sided mattress assembly
supported on
a rigid foundation that offers significant reduction in the amount of
permanent
deflection or sagging of sleeping surface of the mattress.
A conventional inner spring mattress as known in the bedding industry
generally comprises a resilient construction consisting of two sleep surfaces
(a top
layer and a bottom layer) enclosing an assembly of wire springs. The wire
springs are
typically covered with padding layers on the top and bottom surfaces, and the
whole
assembly is encased within a ticking, often quilted, that is sewn closed
around its
periphery to a border or boxing. For many years, one form of spring assembly
construction has been known as Marshall construction. In Marshall
construction,
individual wire coils are each encapsulated in fabric pockets and attached
together in
strings which are arranged to form a closely packed array of coils in the
general size
of the mattress. Examples of such construction are disclosed in U.S. Pat. No.
685,160,
U.S. Pat. No. 4,234,983, U.S. Pat. No. 4,234,984, U.S. Pat. No. 4,439,977,
U.S. Pat.
No. 4,451,946, U.S. Pat. No. 4,523,344, U.S. Pat. No. 4,578,834, U.S. Pat. No.
5,016,305 and U.S. Pat. No. 5,621,935.
Conventionally, inner spring mattresses, with either pocketed coils or
open coils, have had identical top and bottom layers. During normal life of
such
conventional mattresses some degree of permanent deflection, or sag, can
develop in
the mattress surfaces due to compaction of the component padding materials in
the
top and bottom layers. This permanent deflection can interfere with the
mattresses'
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intended function of providing a supportive and resilient sleep surface. Inner
spring
mattress manufacturers recommend periodically rotating and turning over the
mattress
thereby utilizing the top and bottom sleep surfaces in order to counteract,
minimize,
and/or delay the aforementioned permanent deflection or sag. Under continued
use,
this compaction or sag becomes more permanent. The degree of permanent
deflection
is directly related to the type and amount of padding installed both over and
under the
wire spring core assembly. To remedy this shortcoming, manufacturers utilize
materials that produce less permanent compaction. These materials are
generally more
dense but can be less comfortable and more expensive.
Conventional foundations, such as box springs, often contributed to the
problem of sagging by providing a compressible top layer. Any additional
compaction
of the top layer of the foundation contributes to the overall sagging of the
sleeping
surface of the mattress.
Accordingly, it is desirable to provide a bed construction having an
inner spring mattress assembly which exhibits a reduced amount of permanent
deflection due to compaction of padding materials while at the same time
exhibiting
substantial comfort in use. It is further desirable to provide a mattress
assembly that
can be constructed by conventional known manufacturing techniques. Still
further, it
is desirable to provide a mattress assembly that is cost-effective to produce.
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CA 02578984 2007-03-05
SUMMARY OF THE INVENTION
The present invention improves over the prior art by providing a bed
construction
with a one-sided mattress assembly supported on a rigid foundation. The one-
sided mattress
assembly includes a core of wire springs including, but not limited to,
pocketed or open coil
springs. The spring core of the mattress is covered by a layer of resiliently
compressible material
covering the upper sleeping surface thereof The spring core of the mattress is
supported on a
bottom layer constructed of a substantially rigid material that is not
generally compressible. The
core of coil springs is attached to the bottom layer around its periphery. The
rigid bottom layer
of the mattress assures firm support for the coil springs and thereby reduces
sagging that may
result from the springs being poorly supported by the compressible padding
under the springs of
a conventional two-sided mattress.
In connection with the present invention, the padding for the top layer is
selected
to resist permanent compaction or deflection. Moreover, padding is only needed
on the top layer
of the mattress thereby reducing by one-half the amount of padding required.
Consequently, the
mattress construction of the present invention with a padded top layer and a
rigid bottom layer
necessarily reduces the amount of material that is subject to permanent
compaction and therefore
reduces the amount of permanent deflection of the mattress overall.
Maintenance of the mattress
of the present invention by rotating or turning the mattress over is also
avoided.
In order to further reduce sagging of the sleeping surface of the mattress, a
rigid
foundation is provided to give further support to the rigid bottom layer of
the one-sided mattress
and therefore the spring core.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other novel features and advantages of the invention will be
better understood upon a reading of the following detailed description taken
in conjunction with
the accompanying drawings wherein.
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FIG. 1 is an exploded cross-section view of a conventional two-sided inner
spring
mattress;
FIG. 2 is an exploded cross-sectional view of a one-sided inner spring
mattress
constructed according to the principles of the invention;
FIG. 3 is a schematic plan view of a complete assembly of Marshall coils for
use
in the mattress construction according to the present invention illustrated in
FIG. 2;
FIG. 4 is a partial perspective view, partly broken away, of the Marshall coil
assembly illustrated in FIG. 3; and
FIG. 5 is a partially exploded elevation view of a foundation used in
connection
with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Refening now to the drawings, and initially to FIG. 1, a conventional two-
sided
.mattress is illustrated in exploded cross-section and designated generally by
the reference
numeral 10. The conventional mattress 10 includes as a principal component a
wire spring
assembly 12 of Marshall spring coils, as will be described in detail
hereinafter and which
comprises the central core of the mattress 10. The mattress 10 could also
incorporate an
assembly of open coil springs or other wire inner springs. The mattress 10 has
an upper sleep
surface 14 and a lower sleep surface 16, and therefore, is of a conventional
type intended to be
turned over periodically to help minimize compaction of its padding material
and the resulting
sagging of the mattress 10. Padding material 18, which is identical on both
sides 14 and 16
includes a layer of closed-cell foam such as polyurethane. Covering the
material 18, on both
sides of the mattress, is a ticking layer 20 which may be quilted and which
may include
additional foam in a manner well-known in the art. The ticking layers 20 are
fastened such as by
sewing.to a border 22 which extends around the entire periphery of the core 12
of coil springs.
Turning now to FIG. 2, a mattress 30 constructed according to the invention is
shown in exploded cross-section. The mattress 30, like the conventional
mattress 10 illustrated
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in FIG. 1, has a central core 12 of the Marshall coils. The mattress 30,
however, may
have a central core 12 comprising open coil springs or other wire springs. An
upper
sleep surface 34 is formed over the central core 12 by a layer of foam padding
18 and
a layer of ticking 20. In accordance with the invention, however, the mattress
30 has
an underside 36, positioned under the central core 12 and which comprises a
substantially rigid layer 38 of material covered by a thin layer 40 of a non-
woven
sheeting. A border 42 connects the ticking 20 and sheeting layer 40 and
extends
around the periphery of the coil spring assembly 12. A lower border wire 44 is
secured to the coil spring assembly 12 around its periphery as well as to the
layer 38
such as by hog rings 46.
FIGS. 3 and 4 illustrate one form of mattress core 12 of the
aforementioned Marshall coil construction. In this construction, closely
positioned
coil springs are aligned in a string assembly 50 (FIG. 4) wherein individual
springs 52
are each encapsulated within a pocket of 54 of fabric material 56 which may be
sewn
or ultrasonically welded to create the pockets 54 and to create a unitary
Marshall coil
type assembly 12. An example of such construction is more fully disclosed in
U.S.
Pat. No. 5,621,935. A person of ordinary skill in the art will appreciate that
opened
coil springs or other wire springs may be used for the mattress core 12 as
well as
Marshall coil springs.
As previously described, the sleeping surface 34 comprises a layer of
foam padding 18 and a layer of ticking 20. The ticking 20 is of conventional
construction. In accordance with the present invention, however, the foam
padding 18
is specifically selected to provide comfort yet minimize compaction.
Particularly, the
foam padding 18 is a high density polyurethane foam having a density from
about 1.0
lbs./cu. ft to 2.5 lbs./cu. ft. The foam padding 18 also has a firmness in a
range of
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between 10 and 55 ILD, where "ILD" refers to the standard Indented Load
Deflection
test. Within the ranges specified, the foam padding 18 for the sleeping
surface 34 is
selected to provide varying degrees of firmness or softness to accommodate
individual preferences.
The relatively rigid bottom layer 38 is a high density polyurethane
foarn having a density of approximately 1.85 lbs./cu. ft. The bottom layer 38
also has
a firmness above 30 ILD. In practice, an ILD above 55 has proven to be most
effective based on considerations of cost and durability. Other rigid
materials may be
used in place of the bottom layer 38. Such materials may include solid
plastic, wood,
or other nonyielding rigid materials. To the extend such materials for the
bottom layer
38 yield to pressure, such materials must have at least a high degree of
recoverability
once the pressure has been removed so that the materials are not compacted.
Turning to Fig. 5, there is shown a foundation 60 for use in connection
with the construction of a bed in accordance with the present invention. The
most
important aspect of the foundation 60 for the present invention is providing a
rigid top
surface 62 to support the mattress 30 (Fig. 2). Rigid support of the mattress
30 by the
foundation 60 further reduces the amount of sagging of the sleeping surface
34. In
order to achieve rigid support of the mattress 30, the foundation 60 is
constructed in
accordance with the disclosure of commonly assigned United States Patent No.
5,940,908, and particularly Fig. 6 of that patent.
The foundation 60 has a structural frame 64. The structural frame 64
has a rectangular border including a pair of side rails (only rail 66 is shown
in Fig.
5).The side rails may be formed from standard lumber of construction grade in
nominal lx3 size, connected at a head end of the frame 64 by a head end rai168
and at
the foot end of the frame 64 by a foot end rail 70. The end rails 68 and 70
may be
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formed, for example, from a lower 1x2 end filler slat which butts the side
rails in the
plane thereof. Cross slats 72, 74, 76, 78, 80, 82, and 84 are positioned on
the upper
surfaces of the side rails and extend laterally to span the transverse
distance between
the side rails. Optionally, a longitudinally extending center support rail may
be
attached to an undersurface of the head and foot rails 68 and 70 and secured
to an
underside of each of the cross slats 72-84 to provide additional structural
integrity and
strength for the frame 64.
As further illustrated in FIG. 5, it will be seen that cross slats 80, 82,
and 84 are centrally positioned along the length of the frame 64 and have an L-
shaped
cross-section configuration. However, it should be noted that the L-shaped
cross slats
may be positioned elsewhere along the length of the frame 64 or be employed in
a
lesser or a greater number. The L-shaped cross slats 80, 82, and 84 act as
reinforcing
braces or beams to reduce deflection of the frame 64.
As illustrated in FIG. 5, the non-resilient bedding foundation 60 has a
mattress support assembly 86. The mattress support assembly 86 comprises a
plurality
of wire support members 88 supported on and attached to the end rails 68, 70,
and
cross slats 72, 74, 76, 78, 80, 82, and 84. In this embodiment, a top layer 63
is applied
over the assembly 86 and a cover or ticking 90 is provided to form the
exterior
surface for the entire foundation 60. The top layer 63 is similar in
construction and
performance to the bottom layer 38 of the mattress 30. Particularly, the top
layer 63 is
designed to provide a rigid support surface for the mattress 30 with a
firmness above
ILD and specifically above 55 ILD.
The one-sided inner spring mattress 30 constructed according to the
invention offers considerable advantages over prior art conventional two-sided
25 mattresses in terms of reducing the amount of permanent deflection of the
sleeping
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surface due to undesirable compaction of padding materials. Because the
mattress 30
essentially has a 50 percent reduction in padding due to the rigid bottom
layer 38, the
coil assembly 12 does not settle into and compact a lower padding layer as
would
happen with a two-sided mattress of conventional construction having identical
padding layers on both sides. The addition of a rigid foundation beneath the
one-sided
mattress 30 also provides additional support for the coil springs of the
mattress 30 and
thus helps further reduce sagging.
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The one-sided mattress 30 of the invention also offers the advantage of
eliminating maintenance of the mattress by periodically turning it over as is
recommended for
conventional two-sided mattresses. Accordingly, the one-sided mattress 30 is
more convenient
for the consumer to use. Further, the Marshall coil construction or open
spring construction use
conventional materials so that the one-sided mattress 30 may be readily
manufactured by
techniques that are well known in the industry. The foundation 60 likewise can
be constructed
using conventional manufacturing techniques.
While the present invention has been described in connection with certain
embodiments thereof, it will be apparent to those skilled in the art that many
changes and
modifications can be made without departing from the true spirit and scope of
the present
invention. Accordingly, it is intended by the appended claims to cover all
such changes and
modifications as come within the scope of the invention.
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